Data from: Repeatability and contingency in the evolution of a key innovation in phage lambda

The processes responsible for the evolution of key innovations, whereby lineages acquire qualitatively new functions that expand their ecological opportunities, remain poorly understood. We examined how a virus, bacteriophage λ, evolved to infect its host, Escherichia coli, through a novel pathway. Natural selection promoted the fixation of mutations in the virus’s host-recognition protein, J, that improved fitness on the original receptor, LamB, and set the stage for other mutations that allowed infection through a new receptor, OmpF. These viral mutations arose only after the host evolved reduced expression of LamB, whereas certain other host mutations prevented the phage from evolving the new function. This study shows the complex interplay between genomic processes and ecological conditions that favor the emergence of evolutionary innovations.

介导关键创新（key innovations）演化的过程——即谱系（lineages）获得质的全新功能以拓展其生态机遇（ecological opportunities）——迄今仍未得到充分阐明。本研究针对λ噬菌体（bacteriophage λ）如何通过全新通路侵染其宿主大肠杆菌（Escherichia coli）的演化机制展开了探究。自然选择（natural selection）推动了该病毒宿主识别蛋白J中突变的固定，这些突变提升了病毒在原始受体LamB上的适合度（fitness），同时为后续其他允许病毒通过新受体OmpF完成侵染的突变奠定了基础。值得注意的是，这些病毒突变仅在宿主LamB表达量下调后才会出现，而部分宿主突变则会阻碍噬菌体演化出全新的侵染功能。本研究揭示了基因组过程与生态条件间的复杂互作，该互作模式可助力进化创新的产生。